Feeding systems of uninterruptible power supplies include a full-time inverter feeding system and a full-time commercial feeding system (see Japanese Patent Laying-Open No. 2011-223731: PTD 1). In an uninterruptible power supply on a full-time inverter feeding system, during a normal time when AC power is supplied from a commercial AC power source, AC power from the commercial AC power source is converted into DC power by a converter and the DC power is stored in a power storage device. Also, the DC power is converted into AC power by an inverter, so that the converted power is supplied to a load. During a power failure time when supply of AC power from the commercial AC power source is stopped, DC power in the power storage device is converted into AC power by the inverter, so that the converted power is supplied to a load.
In an uninterruptible power supply on a full-time commercial feeding system, during a normal time, AC power from a commercial AC power source is supplied to a load and a bidirectional power converter through a high-speed switch, and is converted into DC power by the bidirectional power converter, so that the converted power is stored in a power storage device. During a power failure time, the high-speed switch is OFF and DC power in the power storage device is converted into AC power by the bidirectional power converter, so that the converted power is supplied to a load.